1. Field of the Invention
This invention relates generally to Voice-over-Broadband (VoB) communication systems, and particularly to diagnostic assessments of the integrity of VoB systems.
2. Discussion of the Prior Art
VoB systems are known in the prior art. VoB system service users are typically referred to as subscribers. FIG. 1 shows a prior art VoB system 100, which commences at one end with traditional Plain Old Telephone Service (POTS) devices 110 that receive and transmit analog voice signals over subscriber lines 115. An Integrated Access Device (IAD) 130 digitizes/packetizes these analog voice signals into a broadband format and integrates the resultant voice packets with additional digital data provided by other customer premise equipment such as personal computer 120. IAD 130 prioritizes voice packets over data packets to preserve transmitted voice signal quality. The voice and data packets are carried over the local broadband access network to an access multiplexer known as a Digital Subscriber Line Access Multiplexer (DSLAM) 140. DSLAM 140 aggregates the packets, transports voice packets to a voice gateway 150 and transports data packets to the Internet 160. Voice gateway 150 depacketizes voice packets and converts them to standard analog POTS signals for delivery via a Class 5 switch 165 to the Public Switched Telephone Network (PSTN) 170.
FIG. 2 shows details of IAD 130. A POTS device 110 connected to the subscriber's line 115 is in turn connected with a Subscriber Line Interface Circuit (SLIC) 210. The SLIC 210 has inputs for a primary battery supply (VBAT1) 220 and an auxiliary battery supply (VBAT2) 230, and has a battery switching circuit 373 (FIG. 5) for connecting to VBAT1 220 to present a high on-hook voltage, and then connecting to VBAT2 230 to present a low off-hook voltage in short-loop applications. VBAT1 and VBAT2 are connected in series by a diode 225. The diode serves as a protection device to prevent the VBAT1 (−68V) supply from going more positive than the VBAT2 (−24V) supply. This would happen if the VBAT1 supply failed, since VBAT1 voltage (−68V) is obtained by adding a −44 voltage to the VBAT2 supply. SLIC 210 passes analog POTS signals to a coder/decoder (CODEC) 240 and receives analog signals from CODEC 240. CODEC 240 converts analog voice signals into broadband digital format, and vice versa. IAD 130 can include a digital signal processor (DSP) 250 for removing noise from the digital signals. Finally, IAD 130 employs a microprocessor controller (MPC) 260 as a central software-driven controller. MPC 260 can manipulate digital signals as necessary per the instructions of an installed software application, can receive state information from the various IAD 130 components, and can send digital control signals to the other components of IAD 130. In particular, MPC 260 sends digital control inputs 270 to SLIC 210, which control internal SLIC states. FIG. 2, for clarity, shows only one POTS port and only the processing of voice data. In practice, an IAD 130 also processes incoming digital data and includes multiple ports (typically in RJ-11 format) for connecting multiple POTS devices 110.
Thus the IAD 130 is a critical component of a VoB system. As VoB systems gain market share in the communications industry, IAD equipment will proliferate and it will become more important that VoB service providers have the ability to efficiently and cost effectively maintain IADs. Additionally, as users of traditional POTS devices shift to VoB service, it will become imperative, for the sake of customer relations, that VoB service providers give useful customer support regarding the low technology POTS devices. POTS devices rely on a simple two-wire loop for all their power and signaling needs and do not provide any diagnostic signaling. Thus, there is a need in the art of VoB communications for diagnostic tests on IAD equipment and POTS devices that do not require additional hardware modifications and associated costs (i.e., abide by the constraints of existing hardware designs) and do not require physical site visits for the purpose of conducting the diagnostic tests.